The invention relates to a method of manufacturing a photomask and a photomask technology, and in particularly to a photomask technology that is effectively applicable to a photomask to be used for photolithography (to be referred to simply as lithography hereinafter) when a predetermined pattern is transferred onto a semiconductor wafer (to be referred to simply as wafer hereinafter).
In methods of manufacturing semiconductor integrated devices, a lithography technology has been used as methods of transferring fine patterns onto wafers. A projection exposure apparatus has been chiefly used in the lithography technology. The pattern of the mask fitted to the projection exposure apparatus is transferred onto a wafer to form a device pattern.
Normal masks are manufactured by processing metal films or inorganic films formed on a transparent mask plate. The metal films have a light blocking effect such as chromium (Cr) or the like. The inorganic films have a light reduction effect or a light blocking effect such as MoSi, ZrSiO, SiN or the like. That is, the above-mentioned ordinary masks are constituted by forming the above-mentioned metal films or inorganic films in desired shapes.
These metal films or inorganic films are normally formed by a sputtering method. The metal films are processed, for example, in a manner as follows. That is, firstly, after a resist film is applied on a metal film, a desired pattern is drawn on the resist film. Subsequently, after resist patterns having a desirable shape are formed by development, the resist patterns are used as a masking layer, and a metal film is processed by dry etching or wet etching. Thereafter, the resist patterns are removed, and cleaning or the like is performed, and the light blocking effect comprising the above-mentioned metal film having a desired shape is formed on a transparent mask plate. An inorganic film is also formed in the same manner.
However, the mask with such the constitution has problems of requiring many manufacturing processes and increasing manufacturing costs thereof. For the purpose of simplicity and lower costs of processes of manufacturing a mask, Japanese Patent Laid-open No. 5-289307 discloses a so-called resist mask method of forming a light shielding film by using a resist film. This method utilizes such a characteristic that an ordinary electron beam sensing resist film or a photosensitive resist film blocks vacuum ultraviolet light having a wavelength of about 200 nm or less. This method does not need the steps of etching light shielding films and of removing resist films, so that it is possible to reduce manufacturing costs of masks and diminish TAT by simplicity of the manufacturing steps. In recent years, as competition for developing semiconductor integrated circuit devices promotes, a plurality of masks is required for acceleration of device debug so that there has arisen needs for manufacturing the masks by low costs. There has also arisen needs for making the masks during TAT (Turn Around Time). Particularly, these needs increase because demand of a minority of various LSIs (Large Scale Integrated circuit) increases. From these views, manufacture of the masks in a short period and reduction of costs thereof are required further.
Meanwhile, in the above-mentioned resist mask technique, inventors of the present invention have found the following drawbacks.
That is, since the light shielding resist film of the above-mentioned resist mask can not obtain satisfactory light blocking effect against light beam having a wavelength of 200 nm or more, there arises a problem of obtaining no satisfactory resolution of the above-mentioned resist mask in exposure treatment using exposure light having a wavelength of 200 nm or more.
An object of the present invention is to provide a technique in which a resist mask having satisfactory resolution can be obtained.
The above object and other objects of the present invention and the novel features of the present invention will become apparent from description of the present specification and the accompanying drawings.
Some of the aspects of the present invention will be briefly summarized below.
According to the invention, a multi-layer attenuation pattern comprising a first organic layer having an attenuation effect relative to light for exposure and a second organic layer having a photosensitive effect relative to light for exposure is formed on a mask plate.
According to the invention, the phase of light for exposure transmitted through the attenuation pattern forming region is inverted relative to the phase of light exposure transmitted through the open regions devoid of the attenuation pattern.
According to the invention, a multi-layer attenuation pattern comprising a first organic layer having a light shielding effect relative to light for exposure and a second organic layer having a photosensitive effect relative to light for exposure is formed on a mask plate.
According to the invention, there is provided a method of manufacturing a photomask having an attenuation pattern and having a multi-layer structure of first and second organic layers, said method comprises: a step of depositing a first organic layer having an attenuation effect relative to light for exposure on a mask plate; a step of depositing a second organic layer having a photosensitive effect relative to light for exposure on the first organic layer; a step of exposing the second organic layer to light with a desired pattern; a step of patterning the second organic layer by developing the second organic layer; and a step of forming an attenuation pattern by patterning the first organic layer, using the patterned second organic layer as masking pattern.
According to the invention, there is also provided a method of manufacturing a photomask having an opaque pattern and having a multi-layer structure of first and second organic layers, said method comprises: a step of depositing a first organic layer having a light shielding effect relative to light for exposure on a mask plate; a step of depositing a second organic layer having a photosensitive effect relative to light for exposure on the first organic layer; a step of exposing the second organic layer to light with a desired pattern; a step of patterning the second organic layer by developing the second organic layer; and a step of forming an opaque pattern by patterning the first organic layer, using the patterned second organic layer as masking pattern.
Further, a photomask is constituted as follows.
(1). A photomask characterized in that an attenuation pattern formed on a mask plate comprises a multi-layer formed by a first organic layer having an attenuation effect relative to exposure light, and a second organic layer having a photosensitive effect relative to exposure light to be used formed a mask pattern.
(2). The photomask according to item (1),
wherein an attenuation pattern comprising the multi-layer formed by said first and second organic layers, and an opaque pattern comprising a metal layer are provided in a pattern transferring region of said mask plate.
(3). The photomask according to item (1),
wherein if refractive index of said second organic layer to exposure light having a wavelength of xcex is n1, and that of the first organic layer is n2, and a film thickness of said second organic layer is d1, and that of said first organic layer is d2, then one of
5/4xe2x89xa6[(n1xe2x88x921)d1+(n2xe2x88x921)d2]/xcexxe2x89xa67/4
xe2x80x83and
9/4xe2x89xa6[(n1xe2x88x921)d1+(n2xe2x88x921)d2]/xcexxe2x89xa611/4
xe2x80x83is satisfied.
(4). A photomask characterized in that an opaque pattern formed on a mask plate comprises a multi-layer formed by a first organic layer having an opaque effect relative to exposure light, and a second organic layer having a photosensitive effect relative to exposure light to be used for exposing a mask pattern.
(5). The photomask according to item (4),
wherein an opaque pattern comprising the multi-layer formed by said first and second organic layers, and an opaque pattern comprising a metal layer are provided in a pattern transferring region of said mask plate.
(6). The photomask according to item (4),
wherein extinction coefficient is 0.02 or more relative to the exposure light of said first organic layer.
(7). A photomask characterized in that an attenuation pattern formed on a mask plate comprises a multi-layer formed by a first organic layer having an attenuation effect relative to exposure light and by a second organic layer having a photosensitive effect relative to exposure light to be used for exposing a mask pattern, and an end portion of the pattern of said second organic layer hangs longer than an end portion of the pattern of said first organic layer.
(8). The photomask according to item (7),
wherein if refractive index of said second organic layer relative to exposure light having a wavelength of xcex is n, a thickness d of said second organic layer satisfies
xcex/(4(nxe2x88x921))xe2x89xa6dxe2x89xa63xcex/(4(nxe2x88x921)).
(9). The photomask according to item (8),
wherein if reduction ratio of a projection lens in an exposure apparatus is 1/M, an overhang amount of said second organic layer is between 0.05/M(xcexcm) and 0.15/M(xcexcm).
(10). The photomask according to item (1),
wherein said first organic layer has a characteristic of absorption of exposure light having a wavelength of 200 nm or more.
(11). The photomask according to item (1),
wherein said exposure light is one of a KrF excimer laser beam, an i-line of an ultra high pressure mercury lamp, and a g-line of an ultra high pressure mercury lamp.
(12). The photomask according to item (1),
wherein an opaque pattern comprising a metal layer is provided in an outer peripheral region of the pattern transferring region of said mask plate.
(13). The photomask according to item (12),
wherein a mark pattern is formed by a light transmitting pattern formed by cutting a portion of the opaque pattern formed of said metal layer.
(14). The photomask according to item (13),
wherein said mark pattern is a reticle alignment mark indicating a position of a photomask to an exposure apparatus.
(15). The photomask according to item (1),
wherein said first and second organic layers are provided so as not to be arrayed in a portion contacting to the other device on said mask plate.
(16). The photomask according to item (1),
wherein said first organic layer is electrically conductive.
(17). The photomask according to item (16),
wherein said first organic layer contains polyaniline.
42. A photomask for exposure, which has a transparent substrate and an attenuation layer for attenuating exposure light, a desired pattern being formed in said attenuation layer, the photomask characterized in that said attenuation layer is formed by sequentially laminating a photo-absorptive organic layer and a photosensitive organic layer, and that light absorbance relative to exposure light of said photo-absorptive organic layer is higher than that of said photosensitive organic layer.
(19). A photomask for exposure, which has a transparent substrate and an attenuation layer for attenuating exposure light, a desired pattern being formed in said attenuation layer, the photomask characterized in that said attenuation layer is formed by sequentially laminating a photo-absorptive organic layer and a photosensitive organic layer, and that if refractive index of said resist layer relative to exposure light having a wavelength of xcex is n, then a thickness d of said photosensitive organic layer satisfies
xcex/(4(nxe2x88x921))xe2x89xa6dxe2x89xa63xcex/(4(nxe2x88x921)).
(20). The photomask according to item (19),
wherein a width of the pattern of said photo-absorptive organic layer is smaller than that of said photosensitive organic layer, and
wherein an end portion of the pattern of said photosensitive organic layer hangs over a rim portion of said desired pattern.
(21). The photomask according to item (20),
wherein if reduction ratio of a projection lens in an exposure apparatus is 1/M, an overhang amount of said photosensitive organic layer is between 0.05/M(xcexcm) and 0.15/M(xcexcm).